Can A Forum USER help with This instruction

I made my order form custom so I don't have to have that popup going on for payment/shipping address.
I have ONE item I am trying to fix.
The email address of the customer is not showing in the "orders" page.
See the attached screen shot, you'll see email addresses at the bottom but orders since then are blank in the customer field.

I asked Nicolas how to change this and his answer was:
It's normal that it is blank.
If you want to display the email custom order field value instead, you will have to edit the file "listing" of the view "order" for your backend template and add the line:
CUSTOM_ORDER_FIELD; ?>

(where CUSTOM_ORDER_FIELD has to be replaced with the column name of your custom order field)

after:

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I wrote back and asked where exactly do I put this

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The answer was after:

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What kind of an answer is that?
Does anyone who has customized their checkout know anything about this?

The answers you get as a business version owner are often sarcastic and they assume you are an expert which I am not.

A LOT of people do NOT like the checkout process and I don't think I am asking too much by wanting a process without stupid popups. Anyone OUTSIDE of Hika Shop with any answers, please let me know. Thanks!